This invention relates to optical sources based on diode laser technology. The present invention relates specifically to a new frequency-selective optical laser source that is electro-optically tunable. It also relates to the development of a single transverse mode laser when excited by a gain region that supports the lasing of many modes (multimode operation). It further relates to the efficient coupling of the output of this laser radiation into single-mode waveguides for subsequent frequency conversion applications.
Power diode lasers are currently commercially available with output power from a single chip in excess of 3 W. The achievement of such high total power in the face of the power density limitation at the facet due to optical damage requires the use of broad area gain sections with emission facet widths of hundreds of microns. These broad area amplification regions inherently allow multiple modes of operation. To limit the operation of these broad area multi-transverse mode diode lasers to a single transverse spatial mode, thus obtaining a diffraction limited output beam, it is necessary to provide some other mechanism to suppress the higher order transverse modes. Achieving frequency control to produce single longitudinal mode operation adds further difficulty. However, many applications require either diffraction limited beams or single frequency beams.